Telephone-transmitter.



A. H. KAHL. TELEPHONE TRANSMITTER. APPucATloN FILED ammo. ma.

Patented J an. 21, 1919.

ARTHUR ROBERT KAI-IL, 0F WITHINGTON, MANCHESTER, ENGLAND.

TELEPHONE-TRANSMITTER.

Specification of Letters Patent.

Patented Jan. 21, 1919.

Application led March 20, 1916. Serial No. 85,247.

To all whom t may concern:

Be it known that I, ,ARTHUR R. KAEL, a citizen of the United States, residing at 59 Burton road, Withington, Manchester', England, have invented certain new and useful Improvements in Telephone-Transmitters, of which the following is a specification.

My invention relates to an improved telephone transmitter construction, in which the main diaphragm is specially shaped and mounted so as to improve the purity of tone of the instrument and eliminate external or improved construction consists in the manner in which the-mica diaphragm of the variable resistance element is clamped, as a result of which the operation of the resistance element is much improved.

My invention will be better understood by reference to the drawings in which- Figure 1 is a longitudinal central sectional view through the transmitter completely assembled, some of the parts being shown in elevation for clearness;

Fig. 2 is a back elevation? of the transmitter with the inclosing shell removed;

Fig. 3 is a longitudinal central sectional view through the variable resistance element of the transmitter; and v Fig.4shows in elevation a spring clamp ing disk employed in connection with the variable resistance element construction.

Similar numerals refer to similar parts throughout the several views.A

The transmitter construction consists'of a front plate 10 formed asindicated of sheet metal, and supporting centrally from its front face a mouthpiece 11 screwed therein. The edge of the front plate 10 is flanged as indicated at 10a to support the inclosing shell 12, which is fastened to the front plate by suitable screws in a manner well known in the art. The fiange 10a is provided at diametrically opposite portions with inturned flanges 10", to which the bridge 13 is screwed as indicated.

The variable resistance element consists essentially of a cup 14 having a central boss 15, into which -is threaded a stud 16, projecting rearwardly from the cup. The circular wall of the cup is internall threaded and engages a threaded ring 1 between which and the cup the rear electrode 18 is A clamped. The outer end of the threaded ring 17 is engaged by the clamping ring 19 provided with an, mturned outer ange for Another feature of myl engaging the outer portion of the delicate mica diaphragm 20 of the variable resistance element and holding it securely against the outer edge of the ring 17. Centrally located in the diaphragm 2O is a screw stud 21, which has rigidly secured to its inner end a metal disk 22, which in turn has secured to its inner face the front electrode 23 of the variable resistance element. Located outside of the diaphragm 20 is a dished spring washer 24, circular in form as' shown in Fig. 4, and made of sufficiently thin spring material, such as brass, German silver or the like so that when it is forcibly clamped against the spacing washer 25 by the nut 26 it will exert a uniform spring tension circumferentially on the diaphragm 20 just inside of the periphery of the disk 22, and thus securely hold the diaphragm at the point where the clamping action is needed without, however, exerting such a rigid clamping effect' as to in any way interfere with the proper operation of the diaphragm. Furthermore, the clamping action is uniformly distributed and is found to give an improved articulation as compared with the rigid clamping construction commonly in use, and furthermore, the tone produced is not as harsh with my construction as with the rigid clamping construction referred to.

The stud 16 projecting from the resistance element is mounted in the bridge 13 as follows: Afirst bushing 27 is supported near the middle portion of said bridge and insulated therefrom, being held in place by a clamping nut 28. This bushing carries a set screw 29, which engages a second bushing 30 contained'in the first bushing, and holds said second bushing `in desired longitudinal adjustment around the stud 16. A' slight clearance is made in the bushing 30 around the lstud 16` for purposes `of adjustment, and

when the parts are properly adjusted this space is filled wholly or in part with solder or cement 31, which rigidly secures the stud 16 to the bushing 30. This particular construction does not form a part of my present invention as it is the subject matter of a copending application, Serial No. 85,246, filed March 20, 1916, and I do not therefore claim this construction in the present application.

The screw stud21 projects through the central portion of the maindiaphragm 32 and is clamped thereto by a nut 33 carried by the outer end of said screw stud, the connector 34beingc1amped between the main f lead ring is made slightly thicker than it is to be in the transmitter, and is forced into place in the flange la by means of a tool having a perfectly fiat face, ina powerful press, the effect being to produce at the same time a perfectly flat surface for receiving the ring Y35 and compress the lead of the ring so as to wedge it into place in the flange a. To insure that the ring 36 is securely held in place against accidental displacement which might result by careless handling of the assembled transmitters, it is preferable to employ a suitable cement between the front plate 10 and the ring, as for example, Sterling insulated varnish, which I find, when properly applied, se cure'ly holds the ring against any handling to which'the transmitter may be subjected.

The lead ring referred to is for the followingV purpose: In constructing transmit ter fronts from sheet material as is now common practice, the thickness of the material can not be great if the metal is to be properly formed by the dies. As a result the front plates readily vibrate under the inluence of external noises, and these vibrations are communicated directly to the main diaphragm, where the telephone construc-y tion is such that the main diaphragm rests directlyA against the front plate or is separated therefrom only by means of hard and resilient material. By my construction the relatively heavy lead ring serves in large measure to prevent theY setting up of these vibrations by materially increasing the effective mass of the front plate, and furthermore, any vibrations that maybe set up in the front plate are not communicated to the main diaphragm, for the reason that the material of the ring 36 is non-resilient, and has no spring or tendency to vibrate. The lead ring therefore serves to form an inert .r dead cushion for the main diaphragm against the effect of noises which may surround the transmitter. The shape of the main diaphragm serves in effect to make the diaphragm a spring, and at the same time gives a large diameter vibration fulcrum to the diaphragm, Which permits its ready viand the connector 34k is connected withthe binding post 39, these binding posts being carried by and insulated from the bridge 13, dampening springs 40 secured to the bridge rest against the rear face of a disk 41 of insulating material, such as empire cloth, which `is placed against the rearA face of the main diaphragm, and all ofthe parts arey inclosed in the shell 12 as indicated in Fig. l.

As a result of my present invention I find I that my improved transmitter operates more quietly and effectively on account of the construction of the main diaphragm and its seat and the manner of clamping the diaphragm of the resistance element, and at the same time the construction is cheaper than many constructions heretofore employed. It is to be borne in mind that the resistance element may be mounted from the bridge in any desired manner, and in connection with my present invention, therefore, I do not limit myself to any particular bridge mounting arrangement, the present construction merely being shown as typical of one such arrangement.

rThe carbon granules commonly employed in telephone transmitters are not shown in the drawings, as their use in variable resistance elements is well known in the art and they require no special illustration on description.

Y- lxhat l claim is: f 'Y l. ln a telephone transmitter, the combination of asheet metal front plate, a ring of heavy non-resilient material secured to the rear face of said front plate, a diaphram resting against the rear face of said `ring, a bridge secured to the front plate, and

a variable resistance element mounted between said bridge and said diaphragm.

2. In a telephone transmitter, the combination of a sheet metal front plate, a lead"- ring secured to said' front plate, a diaphragm pressed against said ring, a bridge carried by said. front plate, anda variable `resistance element mounted between said bridge and said diaphragm. j

3. In a telephone transmitter, the combination of a sheet metal front plate, a ring of heavynon-resilient material secured vto the rear face of said front plate, a dia-- phragm resting against the rearface-of said,

ring, a bridge-secured to thefront plate, and a variable resistance element mounted between said bridge and said' diaphragm, said variable resistance element comprising a cup,

athin diaphragm inclosure for said cup, a

rigid disk on one side of said thin diaphragm, and a dished clamping disk of vthin spring metal held against the other side of said thin diaphragm. f

4. In a telephone transmitter, the combination of a sheet metal front plate, a lead ringsecured to said front plate, .a diaphragm pressed against said ring, a bridge carried by said front plate, and a Variable resistance element mounted between said bridge and said diaphragm, said variable resistance element comprising a cup, a thin diaphragm inclosure for said cup, a rigid disk on one side of said thin diaphragm, and a dished clamping disk of thin spring metal held against the other side of said thin diaphragm.

5. In a telephone transmitter, the combination of a sheet metal front plate, a ring of heavy non-resilient material secured to the rear face of said front plate, a diaphragm resting against the rear face oi said ring, a bridge secured to the front plate, and a variable resistance element mounted between said bridge and said diaphragm, said diaphragm being slightly dished around its outer edge from the plane of said diaphragm.

6. In a telephone transmitter, the combination of a sheet metal front plate, a lead ring secured to said front plate, a diaphragm pressed against said ring, abridge carried by said front plate, and a variable resistance element mounted between said bridge and said diaphragm, said diaphragm being slightly dished around its outer edge from the plane of said diaphragm..

7. In a telephone transmitter, the combination of a sheet metal front plate, a ring of heavy non-resilient material secured to the rear face of said front plate, a diaairafm re infra a'n L.r (ce ai( 1l g st g g1 sttherea fa ofs l ring, a bridge secured to the front plate, and a variable resistance element mounted between said 'bridge and said diaphragm, and cement between said ring and said front plate for holding said ring in place.

8. In a telephone transmitter, the combination of a sheet metal front plate, a lead ring secured to said front plate, a diaphragm pressed againstsaid ring, a bridge carried by said front plate, and a variable resistance element mounted between said bridge and said diaphragm, `and cement between said ring and said front plate for holding said ring in place.

9; In a telephone transmitter, the combination of a sheet metal front plate, a ring of heavy non-resilient material secured to the rear face of said front plate, a diaphragm resting against the rear face of said lring, a bridge secured to the front plate,

` pressed against said ring, a bridge carried by said liront plate, and a variable resistance element mounted between said bridge and said diaphragm, said ring having a compressed rear surface alfording a true seat :tor said diaphragm.

11. In a telephone transmitter, the combination of a sheet metal front plate, a ring of heavy non-resilient material secured to the rear face of said front plate, a diaphragm resting against the rear face of said ring, a bridge secured to the front plate, and a variable resistance element mounted between said bridge and said diaphragm, said ring being held in place in said front plate by compression of the material in said ring.

12. In a telephone transmitter, the combination of a sheet metal front plate, a lead ring secured to said front plate, a diaphragm `pressed against said ring, a bridge carried by said front plate, and a variable resistance element mounted between said bridge and said diaphragm, said ring being held in place in said front plate by compression of the material in said ring.

13. In a telephone transmitter, the combination of a sheet metal front plate, a ring of heavy non-resilient material secured to the rear face of said front plate, a diaphragm resting against the rear face of said ring, a bridge secured to the front plate, and a variable resistance element mounted between said bridge and said diaphragm, said diaphra gm having a small amount of its surface adjacent its outer edge bent forwardly into the frustum of a cone of large angle.

14. In a telephone transmitter, the combination of a sheet metal front plate, a lead ring secured to said front plate, a diaphragm pressed against said ring, a bridge carried by said front plate, and a variable resistance element mounted between said bridge and said diaphragm, said diaphragm having a small amount of its surface adjacent its outer edge bent forwardly into the frustum oi' a cone of large angle.

15. In a telephone transmitter, the combination of a front plate, a bridge secured to the front plate, a variable resistance element mounted upon said bridge, and a diaphragm connected with said variable resistance element, said diaphragm having its edge surface bent forwardly into the frustum of a cone of large angle resting loosely against the rear of said front plate.

16. In a telephone transmitter, the combination of a front plate, a bridge secured to the front plate, a variable resistance element mounted upon said bridge, a diaphragm connected with said variable resistance element, Said diaphragm having its edge surface bent forwardly into the frustum of a @one of large angle resting loosely against the rear of said front plate, and a ring of hard insulating material between the edge of said diaphragm and said front plate. 10

In Witness whereof, I hereunto subscribe my name this 22nd day of February A. D.-

ARTHUR ROBERT KAHL.

Copies of `this patent maybe obtained. for ve cents each, by addressing the Commissioner of Patente. Wahington, D. C. 

